from django.db import NotSupportedError
from django.db.models.expressions import Func, Value
from django.db.models.fields import CharField, IntegerField, TextField
from django.db.models.functions import Cast, Coalesce
from django.db.models.lookups import Transform
class MySQLSHA2Mixin:
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
template="SHA2(%%(expressions)s, %s)" % self.function[3:],
**extra_context,
)
class OracleHashMixin:
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
template=(
"LOWER(RAWTOHEX(STANDARD_HASH(UTL_I18N.STRING_TO_RAW("
"%(expressions)s, 'AL32UTF8'), '%(function)s')))"
),
**extra_context,
)
class PostgreSQLSHAMixin:
def as_postgresql(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
template="ENCODE(DIGEST(%(expressions)s, '%(function)s'), 'hex')",
function=self.function.lower(),
**extra_context,
)
[docs]
class Chr(Transform):
function = "CHR"
lookup_name = "chr"
output_field = CharField()
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
function="CHAR",
template="%(function)s(%(expressions)s USING utf16)",
**extra_context,
)
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(
compiler,
connection,
template="%(function)s(%(expressions)s USING NCHAR_CS)",
**extra_context,
)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="CHAR", **extra_context)
class ConcatPair(Func):
"""
Concatenate two arguments together. This is used by `Concat` because not
all backend databases support more than two arguments.
"""
function = "CONCAT"
def pipes_concat_sql(self, compiler, connection, **extra_context):
coalesced = self.coalesce()
return super(ConcatPair, coalesced).as_sql(
compiler,
connection,
template="%(expressions)s",
arg_joiner=" || ",
**extra_context,
)
as_sqlite = pipes_concat_sql
def as_postgresql(self, compiler, connection, **extra_context):
c = self.copy()
c.set_source_expressions(
[
expression
if isinstance(expression.output_field, (CharField, TextField))
else Cast(expression, TextField())
for expression in c.get_source_expressions()
]
)
return c.pipes_concat_sql(compiler, connection, **extra_context)
def as_mysql(self, compiler, connection, **extra_context):
# Use CONCAT_WS with an empty separator so that NULLs are ignored.
return super().as_sql(
compiler,
connection,
function="CONCAT_WS",
template="%(function)s('', %(expressions)s)",
**extra_context,
)
def coalesce(self):
# null on either side results in null for expression, wrap with coalesce
c = self.copy()
c.set_source_expressions(
[
Coalesce(expression, Value(""))
for expression in c.get_source_expressions()
]
)
return c
[docs]
class Concat(Func):
"""
Concatenate text fields together. Backends that result in an entire
null expression when any arguments are null will wrap each argument in
coalesce functions to ensure a non-null result.
"""
function = None
template = "%(expressions)s"
def __init__(self, *expressions, **extra):
if len(expressions) < 2:
raise ValueError("Concat must take at least two expressions")
paired = self._paired(expressions, output_field=extra.get("output_field"))
super().__init__(paired, **extra)
def _paired(self, expressions, output_field):
# wrap pairs of expressions in successive concat functions
# exp = [a, b, c, d]
# -> ConcatPair(a, ConcatPair(b, ConcatPair(c, d))))
if len(expressions) == 2:
return ConcatPair(*expressions, output_field=output_field)
return ConcatPair(
expressions[0],
self._paired(expressions[1:], output_field=output_field),
output_field=output_field,
)
[docs]
class Left(Func):
function = "LEFT"
arity = 2
output_field = CharField()
def __init__(self, expression, length, **extra):
"""
expression: the name of a field, or an expression returning a string
length: the number of characters to return from the start of the string
"""
if not hasattr(length, "resolve_expression"):
if length < 1:
raise ValueError("'length' must be greater than 0.")
super().__init__(expression, length, **extra)
def get_substr(self):
return Substr(self.source_expressions[0], Value(1), self.source_expressions[1])
def as_oracle(self, compiler, connection, **extra_context):
return self.get_substr().as_oracle(compiler, connection, **extra_context)
def as_sqlite(self, compiler, connection, **extra_context):
return self.get_substr().as_sqlite(compiler, connection, **extra_context)
[docs]
class Length(Transform):
"""Return the number of characters in the expression."""
function = "LENGTH"
lookup_name = "length"
output_field = IntegerField()
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(
compiler, connection, function="CHAR_LENGTH", **extra_context
)
[docs]
class LPad(Func):
function = "LPAD"
output_field = CharField()
def __init__(self, expression, length, fill_text=Value(" "), **extra):
if (
not hasattr(length, "resolve_expression")
and length is not None
and length < 0
):
raise ValueError("'length' must be greater or equal to 0.")
super().__init__(expression, length, fill_text, **extra)
[docs]
class Ord(Transform):
function = "ASCII"
lookup_name = "ord"
output_field = IntegerField()
def as_mysql(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="ORD", **extra_context)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="UNICODE", **extra_context)
[docs]
class Repeat(Func):
function = "REPEAT"
output_field = CharField()
def __init__(self, expression, number, **extra):
if (
not hasattr(number, "resolve_expression")
and number is not None
and number < 0
):
raise ValueError("'number' must be greater or equal to 0.")
super().__init__(expression, number, **extra)
def as_oracle(self, compiler, connection, **extra_context):
expression, number = self.source_expressions
length = None if number is None else Length(expression) * number
rpad = RPad(expression, length, expression)
return rpad.as_sql(compiler, connection, **extra_context)
[docs]
class Replace(Func):
function = "REPLACE"
def __init__(self, expression, text, replacement=Value(""), **extra):
super().__init__(expression, text, replacement, **extra)
[docs]
class Reverse(Transform):
function = "REVERSE"
lookup_name = "reverse"
def as_oracle(self, compiler, connection, **extra_context):
# REVERSE in Oracle is undocumented and doesn't support multi-byte
# strings. Use a special subquery instead.
suffix = connection.features.bare_select_suffix
sql, params = super().as_sql(
compiler,
connection,
template=(
"(SELECT LISTAGG(s) WITHIN GROUP (ORDER BY n DESC) FROM "
f"(SELECT LEVEL n, SUBSTR(%(expressions)s, LEVEL, 1) s{suffix} "
"CONNECT BY LEVEL <= LENGTH(%(expressions)s)) "
"GROUP BY %(expressions)s)"
),
**extra_context,
)
return sql, params * 3
[docs]
class Right(Left):
function = "RIGHT"
def get_substr(self):
return Substr(
self.source_expressions[0],
self.source_expressions[1] * Value(-1),
self.source_expressions[1],
)
[docs]
class SHA1(OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = "SHA1"
lookup_name = "sha1"
[docs]
class SHA224(MySQLSHA2Mixin, PostgreSQLSHAMixin, Transform):
function = "SHA224"
lookup_name = "sha224"
def as_oracle(self, compiler, connection, **extra_context):
raise NotSupportedError("SHA224 is not supported on Oracle.")
[docs]
class SHA256(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = "SHA256"
lookup_name = "sha256"
[docs]
class SHA384(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = "SHA384"
lookup_name = "sha384"
[docs]
class SHA512(MySQLSHA2Mixin, OracleHashMixin, PostgreSQLSHAMixin, Transform):
function = "SHA512"
lookup_name = "sha512"
[docs]
class StrIndex(Func):
"""
Return a positive integer corresponding to the 1-indexed position of the
first occurrence of a substring inside another string, or 0 if the
substring is not found.
"""
function = "INSTR"
arity = 2
output_field = IntegerField()
def as_postgresql(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="STRPOS", **extra_context)
[docs]
class Substr(Func):
function = "SUBSTRING"
output_field = CharField()
def __init__(self, expression, pos, length=None, **extra):
"""
expression: the name of a field, or an expression returning a string
pos: an integer > 0, or an expression returning an integer
length: an optional number of characters to return
"""
if not hasattr(pos, "resolve_expression"):
if pos < 1:
raise ValueError("'pos' must be greater than 0")
expressions = [expression, pos]
if length is not None:
expressions.append(length)
super().__init__(*expressions, **extra)
def as_sqlite(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="SUBSTR", **extra_context)
def as_oracle(self, compiler, connection, **extra_context):
return super().as_sql(compiler, connection, function="SUBSTR", **extra_context)
Jan 15, 2024